• David Chinner's avatar
    [XFS] Don't initialise new inode generation numbers to zero · 359346a9
    David Chinner authored
    When we allocation new inode chunks, we initialise the generation numbers
    to zero. This works fine until we delete a chunk and then reallocate it,
    resulting in the same inode numbers but with a reset generation count.
    This can result in inode/generation pairs of different inodes occurring
    relatively close together.
    Given that the inode/gen pair makes up the "unique" portion of an NFS
    filehandle on XFS, this can result in file handles cached on clients being
    seen on the wire from the server but refer to a different file. This
    causes .... issues for NFS clients.
    Hence we need a unique generation number initialisation for each inode to
    prevent reuse of a small portion of the generation number space. Use a
    random number to initialise the generation number so we don't need to keep
    any new state on disk whilst making the new number difficult to guess from
    previous allocations.
    SGI-PV: 979416
    SGI-Modid: xfs-linux-melb:xfs-kern:31001a
    Signed-off-by: default avatarDavid Chinner <dgc@sgi.com>
    Signed-off-by: default avatarChristoph Hellwig <hch@infradead.org>
    Signed-off-by: default avatarLachlan McIlroy <lachlan@sgi.com>
xfs_ialloc.c 42.1 KB